1. Field of the Invention
The present invention relates generally to a circumferential sealing apparatus and, more specifically, to a spool valve sealing cage which comprises a plurality of 0-ring seals and generally rigid cages aligned axially with a common central axis.
2. Description of the Prior Art
It is well known to those skilled in the art to incorporate a plurality of O-ring seals and generally rigid cages, in alternating association with each other, to define a generally cylindrical apparatus in which a spool is disposed for axial movement. The O-ring seals prevent fluid from passing from one region to another along the length of the cylindrical association of cages and seals. The cylindrical assembly of cages and seals is disposed about a central axis and a generally cylindrical spool member is slidably arranged within the cylindrical assembly and in coaxial and concentric association with the cylindrical assembly of cages and seals.
Since a plurality of cages and seals are required to construct the cylindrical sealing apparatus, the tolerance stackup of the assembly can adversely affect its length. Since the assembly is disposed between two stationary locations within the valve body which define the limit of its axial length, variations in the individual axial dimensions of the cages and seals can affect the axial forces exerted by the cages on the seals, which are generally made of an elastomeric material. These forces can result in axial compression of the O-ring seals. The axial compression can seriously affect the radial dimensions of both the inside and outside diameters of the O-ring seals.
It would therefore be significantly beneficial if a sealing apparatus can be provided which avoids the disadvantageous radial effects caused by the tolerance stackup of axial dimensions.